

package com.hazelcast.map.impl.iterator;

import com.hazelcast.internal.util.ConstructorFunction;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * Base class for iterating map entries in the whole cluster with
 * a {@link com.hazelcast.query.Predicate} and a {@link com.hazelcast.projection.Projection}.
 *
 * @param <R> return type of the iterator
 * @see AbstractMapQueryPartitionIterator
 */
public class AbstractMapQueryIterator<R> implements Iterator<R> {

    private final ConstructorFunction<Integer, Iterator<R>> createPartitionIterator;
    private final int partitionCount;
    private Iterator<R> it;
    private int idx;

    public AbstractMapQueryIterator(ConstructorFunction<Integer, Iterator<R>> createPartitionIterator, int partitionCount) {
        this.createPartitionIterator = createPartitionIterator;
        this.partitionCount = partitionCount;
        idx = 0;
        it = createPartitionIterator.createNew(idx);
    }

    @Override
    public R next() {
        if (hasNext()) {
            return it.next();
        }
        throw new NoSuchElementException();
    }

    @Override
    public boolean hasNext() {
        while (!it.hasNext()) {
            if (idx == partitionCount - 1) {
                return false;
            }
            it = createPartitionIterator.createNew(++idx);
        }
        return true;
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException("Removing when iterating map with query is not supported");
    }
}
